Image sensors, used in digital cameras, are optionally designed with multiple outputs to increase frame rate. However, multiple outputs introduce non-uniformities due to the mismatches in performance of the separate outputs and associated off-chip signal processing hardware. It has been practiced (for example U.S. Pat. No. 6,072,603) that the mismatches in the output performance can be balanced by the use of known test targets in conjunction with one or more sets of measured correlation values. In these cases, the calibration is static in that it is performed before the image sensor is put into general use and therefore becomes less accurate as environmental or operating conditions change. As these conditions change, the user must re-calibrate the system by generating a new set of correlation values using the test target setup.
Consequently, a need exists for an image sensor which permits real-time calibration.